The best way to do this is to have 9 players in your available players list, and to us the strictly follow depth chart option, and to set each of your trainees for starter backup and reserve at the training position for each one of the games. Here's an example for 1 pos OD training with player 1 as the trainee.
Pos- Starter, backup, reserve
PG- Player 1, Player 1, Player 1
SG- Player 2, Player 3, Player 3
SF- Player 4, Player 5, Player 5
PF- Player 6, Player 7, Player 7
C- Player 8, Player 9, Player 9
The next game, you would do the same thing but with your other trainee in all three PG slots. And be sure to use strictly follow depth chart, or your coach will sub out your player as he pleases. If you use this, all 3 players will get 48+, unless there is an injury or foul-out.
Hope this helps.